This invention relates to systematic interleavers and deinterleavers that are used in conjunction with error correcting coders.
Communication of signals invariably must deal with transmission of signals through noisy channels where errors are introduced. FIG. 1 presents the block diagram of a fairly sophisticated prior art arrangement for such an environment, where data is first applied to encoder 100, the encoded data is passed on to interleaver 200, the interleaved data is modulated in block 300 and the modulated data is applied to the channel. The signal provided by the channel is demodulated in block 400, deinterleaved in block 500 and decoded in block 600.
Interleaver 200 is interposed in the system in order to account for burst errors in the channel. Specifically, interleaver 200 disperses adjacent signal elements in time prior to modulation, that burst errors do not affect too many adjacent signal elements of the original uninterleaved signal. Conversely, when considering the signal coming from the channel, errors that are closely spaced in time are interspersed at the output and are, therefore, far apart from each other. The consequence of this dispersing is that decoder 600 is able to recover the data entered into encoder 100 by virtue of the error-correcting redundancy included in the signal which decoder 600 utilizes.
As is well known, modulator 300 and demodulator 400 may be subsystems that themselves include robust coding and decoding. For example, modulator 300 may include a front end section that is a trellis encoder. Correspondingly, the tail-end of demodulator 400 would include a Viterbi decoder.